Loop 1604, also known as the Charles W. Anderson Loop, is a highway loop that encircles San Antonio, Texas, spanning approximately 95.6 miles (153.9 km). Its outer loop encircles most of San Antonio and its inner loop, Interstate 410, connects with many highways in the city. Loop 1604 began as a two-lane highway and has been upgraded to a four-lane freeway along its northern stretches.